Des anticorps

Researchers at Johns Hopkins report they have identified a protein that enables a toxic natural aggregate to spread from cell to cell in a mammal's brain -- and a way to block that protein's action. Their study in mice and cultured cells suggests that an immunotherapy already in clinical trials as a cancer therapy should also be tested as a way to slow the progress of Parkinson's disease, the researchers say.

A report on the study appears Sept. 30 in the journal Science.

Ted Dawson, M.D., Ph.D., director of the Institute for Cell Engineering at the Johns Hopkins University School of Medicine and one of the study's leaders, says the new findings hinge on how aggregates of α-synuclein protein enter brain cells. Abnormal clumps of α-synuclein protein are often found in autopsies of people with Parkinson's disease and are thought to cause the death of dopamine-producing brain cells.

A few years ago, Dawson says, a researcher at Goethe University in Germany published evidence for a novel theory that Parkinson's disease progresses as α-synuclein aggregates spread from brain cell to brain cell, inducing previously normal α-synuclein protein to aggregate, and gradually move from the "lower" brain structures responsible for movement and basic functions to "higher" areas associated with processes like memory and reasoning. "There was a lot of skepticism, but then other labs showed α-synuclein might spread from cell to cell," Dawson says. Intrigued, his research group began working with those of Valina Dawson, Ph.D., professor of neurology, and Han Seok Ko, Ph.D., assistant professor of neurology, to investigate how the aggregates enter cells.

The researchers knew they were looking for a certain kind of protein called a transmembrane receptor, which is found on the outside of a cell and works like a lock in a door, admitting only proteins with the right "key." They first found a type of cells α-synuclein aggregates could not enter -- a line of human brain cancer cells grown in the laboratory. The next step was to add genes for transmembrane receptors one by one to the cells and see whether any of them allowed the aggregates in. Three of the proteins did, and one, LAG3, had a heavy preference for latching on to α-synuclein aggregates over nonclumped α-synuclein.

The team next bred mice that lacked the gene for LAG3 and injected them with α-synuclein aggregates. "Typical mice develop Parkinson's-like symptoms soon after they're injected, and within six months, half of their dopamine-making neurons die," Dawson says. "But mice without LAG3 were almost completely protected from these effects." Antibodies that blocked LAG3 had similar protective effects in cultured neurons, the researchers found.

"We were excited to find not only how α-synuclein aggregates spread through the brain, but also that their progress could be blocked by existing antibodies," says Xiaobo Mao, Ph.D., a research associate in Dawson's laboratory and first author on the study.

Dawson notes that antibodies targeting LAG3 are already in clinical trials to test whether they can beef up the immune system during chemotherapy. If those trials demonstrate the drugs' safety, the process of testing them as therapeutics for Parkinsons' disease might be sped up, he says.

For now, the research team is planning to continue testing LAG3 antibodies in mice and to further explore LAG3's function.

More than 1 million people in the United States live with Parkinson's disease. The disease gradually strips away motor abilities, leaving people with a slow and awkward gait, rigid limbs, tremors, shuffling and a lack of balance. Its causes are not well-understood.

An international team of scientists has shown that an antibody against the protein EphA3, found in the micro-environment of solid cancers, has anti-tumor effects.

As EphA3 is present in normal organs only during embryonic development but is expressed in blood cancers and in solid tumors, this antibody-based approach may be a suitable candidate treatment for solid tumors.

The researchers from Monash University and Ludwig Cancer Research, in Australia, and KaloBios Pharmaceuticals, in the US, have had their findings published in the journal Cancer Research.

The team, led jointly by the late Professor Martin Lackmann, from the School of Biomedical Sciences at Monash; and Professor Andrew Scott, from Ludwig Cancer Research, has found that even if tumor cells do not have this molecule they can thrive by recruiting and taking advantage of supporting EphA3-containing cells in the tumor micro-environment.

First author, Dr Mary Vail, Monash Department of Biochemistry and Molecular Biology said: "The tumor cells send out signals to the surrounding area and say: 'We need a blood supply and a foundation upon which to spread'."

"We have shown that EphA3 expressing stromal stem cells, which are produced by the bone marrow, form cells that support and create blood vessels in tumors," Dr Vail said.

Professor Andrew Scott's team at Ludwig introduced human prostate cancer cells into a mouse model to mimic disease progression in humans. EphA3 was found in stromal cells and blood vessels surrounding the tumor.

They also observed that treatment with an antibody against EphA3 (chIIIA4) significantly slowed tumor growth. The antibody damaged tumor blood vessels and disrupted the stromal micro-environment, and cancer cells died because their 'life-support' was compromised.

"Our research findings indicate that the tumor micro-environment is important, and monoclonal antibodies against EphA3 are one way to target and kill a variety of solid tumors as well as blood cancers."

Currently, KaloBios Pharmaceuticals is testing the anti-EphA3 antibody KB004 in a multi-centre Phase I/II clinical trial in Melbourne and the US in patients with EphA3 expressing blood malignancies: AML, MDS and myelofibrosis.

Dr Vail, who collaborated with her former mentor on the project for 10 years, said this research represented Martin Lackmann's life work.

"Martin was dedicated to helping people, and believed that KB004 was a promising therapeutic approach. He rightly anticipated that it would be well-tolerated in cancer patients, and through this collaborative project, his pioneering research has progressed to clinical trials and potentially new treatments for cancer patients," Dr Vail said.

Nov. 8, 2013 — A cellular pathway interaction known as TWEAK-Fn14, often associated with repair of acute injuries, also is a viable target for drug therapy that could prevent the spread of cancer, especially brain cancer, according to a study led by the Translational Genomics Research Institute (TGen).

TWEAK is a cytokine, or soluble protein, that controls many cellular activities and acts by binding to a cell surface receptor known as Fn14. TWEAK binding to Fn14 triggers a wide range of cellular activities, including blood clotting, inflammation, cell proliferation, cell migration, and the creation of new blood vessels.

While many of these activities are beneficial -- for example, helping to heal a cut -- excessive TWEAK-Fn14 activation also has been linked to tissue damage and degradation, including autoimmune diseases, as well as the survival, migration and invasion of cancer cells.

"Our results show that the TWEAK-Fn14 interaction is a viable drug target, and they provide the foundation for further exploration of this system in researching invasive cancers," said Dr. Nhan Tran, an Associate Professor in TGen's Cancer and Cell Biology Division.

"Because of its unique qualities and association with acute injuries, this drug-like molecule not only could benefit cancer patients, but also might be applied to patients with autoimmunity, heart disease like atherosclerosis, and rheumatoid arthritis," said Dr. Tran, the study's senior author.

The study, "Structural Basis and Targeting of the Interaction between Fibroblast Growth Factor-Inducible 14 and Tumor Necrosis Factor-like Weak Inducer of Apoptosis" was published in The Journal of Biological Chemistry.

Overexpression of TWEAK-Fn14 has been linked to several types of cancer, including breast, pancreatic, esophageal, lung, liver and -- most important in this study -- glioblastoma.

By using protein-protein docking models, 129 small molecules were selected for screening, which identified four that inhibited the binding of TWEAK to Fn14.

"The next step will be to move this compound forward for drug development and eventual testing in clinical trials, where it might bring immediate benefit for patients," said Dr. Berens, a co-author of the study.

(Nov. 6, 2012) — A newly developed antibody targeting a signalling pathway that is frequently active in solid tumours has shown encouraging signs of efficacy in its first trial in humans, researchers will report at the 24th EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics in Dublin, Ireland, on November 7.

A patient with advanced malignant melanoma has shown signs of tumour shrinkage and has been receiving treatment for more than 30 weeks without any serious adverse side-effects. Other patients with advanced non-small cell lung cancer (NSCLC), mesothelioma, kidney cancer and biliary tract cancer also have had extended treatments with stable disease.

The compound is a monoclonal antibody known as RG7212. It targets a soluble protein in the blood called TWEAK (Tumour Necrosis Factor (TNF)-like weak inducer of apoptosis. TWEAK binds to the receptor Fn14 (fibroblast growth factor-inducible 14) on the cell membrane, and this is the signal for a cascade of subsequent events, including activation of multiple cancer-promoting pathways. One objective of this phase I trial was to determine whether blocking of TWEAK-Fn14 signalling with RG7212 would reduce activation of these pathways.

Dr Ulrik Lassen (MD, PhD), head of the oncology phase I unit at the Rigshospitalet, Copenhagen, Denmark, will tell the Symposium: "TWEAK and Fn14 are a pair of cell signalling molecules that are part of the large family of tumour necrosis factors that play a number of roles in the development of cancer. The Fn14-receptor is over-expressed in a variety of advanced solid tumours, and signalling through TWEAK-Fn14 enhances multiple processes associated with malignancy.

"Preclinical data have shown that the RG7212 monoclonal antibody successfully targets and blocks the action of TWEAK and that it works most effectively in tumour cells where there is increased Fn14 expression. Therefore, we expected that using RG7212 to block TWEAK signalling in patients whose tumours express Fn14 might prevent cancer cells from growing and proliferating."

From July 2011, Dr Lassen and his colleagues recruited 38 patients with treatment-refractory solid tumours to the phase I trial. All patients had tumours expressing the Fn14 receptor. They received an intravenous dose of the drug either once weekly or once every three weeks, with a dose range of 200 to 3600 mg.

Dr Lassen said: "Several of the patients continue to receive study treatments, and encouraging signs of clinical benefit have already been observed. A patient with heavily pre-treated, metastatic melanoma with no mutation in the BRAF gene has shown evidence of tumour regression when scanned using computerised tomography (CT) and remains on study after more than 30 weeks of treatment. Four other patients have had partial metabolic responses confirmed by positron emission tomography (PET) scans.

"Prolonged stable disease has been seen in several patients. Overall, 11 of the 38 patients (29%) have received more than 12 weeks of study treatment, with several receiving 18 or more weeks of RG7212 therapy, including those with refractory NSCLC, melanoma, mesothelioma, breast cancer, renal cell carcinoma, and biliary tract cancer.

"Une stabilisation de la maladie a été observé chez plusieurs patients. 11 des 38 patients ont reçu plus de 12 semaines de traitements, avec plusieurs recevant 18 semaines ou plus de thérapie avec RG7212." "We found that RG7212 has an excellent safety profile across a broad dose range on each schedule. We saw no dose-limiting toxicities and no patient discontinued study treatments for treatment-related adverse side-effects. The phase I data show that RG7212 is quite safe for multi-cycle administration in patients with advanced cancer. Results from tests of blood and tumour samples suggest that it would be feasible to administer the drug over a prolonged period of time.

"There are encouraging pharmacodynamic data (effects of the drug on tumour and blood samples), including durable inhibition of TWEAK, inhibition of signalling pathways controlled by Fn14, and inhibition of tumour cell proliferation."

Study investigators from four leading cancer research centres in Denmark, The Netherlands and Canada are recruiting patients to the trial, particularly those with advanced metastatic melanoma expressing Fn14. "These results are encouraging and support additional studies of RG7212 in combination with other treatments," said Dr Lassen.

Professor Stefan Sleijfer, the scientific chair of the EORTC-NCI-AACR Symposium, from Erasmus University Medical Centre (The Netherlands), commented: "Fn14 is a novel target for treatment in cancer. In view of these data, this drug certainly deserves further studies in Fn14 expressing tumours."